The use of a hand tool to tighten a band clamp has long been known. Band clamps are typically used to secure bundles of materials together and to secure pipes, wiring, etc. In one such application, a band clamp is applied to secure a protective metal braiding around a bundle of wiring which is connected to a plug or coupler known as a back shell.
Back shells are frequently used in military and aerospace applications where wiring carrying low voltage signals are conducted. Both the cables and the connectors must be protectively covered with a metallic substance to limit the harmful effects of radiation thereon. This metallic shielding must be without any "windows" (openings) and must in all parts have a ground connection with only low resistance to effectively minimize any electrical potential this "shielding" system may receive due to external or internal electromagnetic radiation (such as radio emission, cosmic rays, lightning strike, explosion of an atomic device, etc.). The diameter of the back shell body is typically larger than the diameter of the cable entering thereinto, and in order to have a satisfactory interconnection, a banding tool must be capable of applying a band clamp proximate the intersection of the back shell body and the cable, entry stem. Thus the banding tool should be approximately the same width as the band clamp to be applied and should be capable of applying the band clamp from any direction.
One tool for tightening band clamps to a back shell is disclosed in U.S. Pat. No. 4,726,403, to Young et al., Feb. 23, 1988. The Young et al. device uses a toggle arrangement to tension the band clamp in place. Upon reaching the appropriate tension in the band clamp, the tool locks in a closed condition. To sever the tail from the tightened band clamp, a cutting arm must be rotated outwardly and upwardly from the side of the banding tool.
Due to the externally attached cutting device, the Young et al. banding tool is capable of applying a band clamp close to the back shell from only one direction. If a band is attempted to be connected from the opposite direction, the cutting device may prevent proper installation. The Young et al. tool is therefore limited in its application and becomes difficult to operate in confined spaces such as are found in aircraft fuselages.
Additionally, Young's tool uses toggles to transfer tension and toggles generally have a short power stroke in order to make the tool usable by an average person. Therefore, a larger size tool is required to sufficiently tension the band.
Another banding tool is disclosed in U.S. Pat. No. 4,928,738 to Marelin et al., May 29, 1990, assigned to the same assignee as the present invention. The '738 tool uses toggles to provide the power stroke and counteracting springs to achieve the desired tension in a band. It is necessary to force the band to bend around internal portions of the tool during tensioning. Additionally, the tool is not designed with overall width as a primary consideration.
Still another banding tool is disclosed in U.S. Pat. No. 2,087,655 to Prestwich, Jul. 20, 1937, the '655 device has a gripper section which holds one end of the band to be tensioned while a tensioning section grips and pull the other end of the band. The tensioning section comprises a double set of knurled wheels with a first set fixed and a second set movable. While the first set prevents slippage of the band, the second set tensions the band. While there is an angle between the tensioning section and the gripper section, this angular relationship does not provide the advantages of the present invention. Thus there is a need for a method and apparatus to allow tensioning of a band clamp to a back shell from either direction.
An additional concern is the lock established between the band and the buckle of a band clamp. Particularly, the type of lock that is of concern is one in which the free end of a band, whose other end is operatively attached to a buckle, is wrapped about an object and inserted through a passageway extending through the buckle and then bent to create a surface which engages the exterior of the buckle preventing the band from pulling back through. The lock itself is defined by the engagement of the band to the exterior of the buckle. For example, in one lock of this type known to those skilled in the art, the lock is formed by bending the band transverse to the length of the band and away from the object about which the band clamp is wrapped to create the surface, a lip, which engages the upper exterior surface of the buckle to lock the band in place.
The known locks of the type that are formed by bending the band to create a surface that engages the exterior surface of the buckle suffer from many deficiencies and inadequacies. Particularly, a problem prevalent among known locks of this type is their lack of holding power in certain circumstances. One such circumstance is when the lock is used to secure a band clamp about an object which is capable of expansion and contraction. In this situation, the known locks of the aforementioned type are susceptible to failure upon expansion of the object. Consequently, there is a need for a lock of the aforementioned type that exhibits improved strength in these and like circumstances.
A further problem of known locks of the stated type is the force required of the banding tool to create the lock. In many instances, the force necessary to create the locks necessitates the use of a power tool or if a hand tool is employed, considerable force must typically be applied by the operator. For example, in the lock in which the band is bent transverse to its longitudinal axis and away from the object about which the band clamp is wrapped, the devices presently used to shear off the excess band make the entire cut at one time. Further, the force necessary to make the entire cut at once increases as the width of the band increases and as the thickness of the band increases. However, the use of a power tool is not practical in many applications. Similarly, in many situations it is not possible for an operator to apply the requisite force to a hand tool. Consequently, there is a further need for a lock that can be readily formed with hand banding tools.
An additional problem in the aforementioned type of lock is its susceptibility to snagging. Specifically, the known locks of this type are formed in a manner in which they are susceptible to failure due to edges of the lock snagging on articles that can destroy the lock between the band and the buckle by "unbending" the band. For example, the lock formed by bending the band transverse to its longitudinal axis typically has an exposed edge where the excess band has been sheared that is readily snagged. Further, the snagged edge of the lock may damage the material or object that has been snagged. As is apparent, there is a further need for a lock of the defined type that is less susceptible to snagging.
A further problem in the known locks of the aforementioned type is their susceptibility to tampering. For example, the known lock in which the edge of the band is bent away from the object about which the band is wrapped can be defeated with simple tools, such as a pair of pliers, and by hand in some instances. Therefore, there is an additional need for a lock of the defined type that is less susceptible to tampering.
A further problem for locks of the aforementioned type, and especially those in which the band is bent transverse to the length of the band to create a lip that engages the upper exterior surface of the buckle, is that the tool which is used to create the lock and the clamped object must be rotated relative to one another to form the lip. During this rotation process, it is necessary to release some of the tension in the band to prevent the portion where the lock is to be established from thinning or breaking. Hence there is a need for a lock that can be formed while substantially avoiding having to release tension in the band, relative rotation between the band and the clamped object, or thinning of the band in the lock area due to rotation. Concomitantly, there is a need for a tool for forming such a lock.
A further problem of the known locks of the aforementioned type is the inability of one banding tool to create the locks with various widths of the band. Consequently, a separate banding tool must be acquired for each width of band and associated buckle that is employed. Hence, there is a need for a lock that can be formed in band clamps of varying widths by one banding tool.
An additional problem of the known locks is their relative short life. Band clamps are often used in circumstances where they are unprotected from various elements, including the weather, and under great force. In these circumstances, the formation of known locks do not provide the long-life characteristics desired.
A further problem of the known locks is the difficulty in forming a proper lock in circumstances wherein the bundle or object sought to be secured is, for example, at a remote location. The known locks are inadequately designed to be formed by hand-held tools as opposed to machine tools, due to the forces required to form the lock.
Based on the foregoing, there exists a need for an improved lock for a band clamp that is of the type in which the band is bent to form a surface that engages the exterior surface of the buckle and method for making same that exhibits improved strength characteristics. Among other things, there exists a need for a lock of this type that exhibits improved strength characteristics, that can be readily made with hand tools as well as mechanized tools, that is less susceptible to snagging, that is tamper resistant, that permits a single tool to be used to create a lock in band clamps of different widths, and that can be formed while substantially avoiding the release of any tension in the band, relative rotation in the band, rotation between the band and the clamped object, or thinning of the buckle. Moreover, there is a need for a tool and method for forming such a lock.